A conventional shoe made today typically has three major components, as follows.
(1) The upper: This component entity is an assembly which holds and conforms to the shape of the person's foot. The traditional purpose of the shoe upper is to fit the foot properly, comfortably, and snuggly. Ideally, this upper portion of the shoe will also be aesthetically pleasing, be comfortable, and be highly durable.
(2) The Outsole: This component entity is the lower exterior and bottom component of the shoe; and is typically joined to the exterior surface of the shoe upper directly using adhesives or other bonding techniques. The outsole typically is constructed of a durable material or combination of different materials such as rubber or rubber derivatives, and whose purpose is to provide both traction and exterior protection for the wearer's foot.
(3) The insole: This component entity, sometimes referred to as a “sock liner”, is a layer of material inserted into the interior of the upper shoe assembly; is visible to the naked eye when viewing the interior of the footwear; and typically is the exposed surface and material layer upon which the person's foot is physically placed. The purpose and function of the insole is to provide an additional layer of shock absorbing material directly under the foot within the upper and/or to provide some arch support for the foot while wearing the shoe.
In addition, certain shoes, such as athletic shoes, are considered to contain a “midsole.” Although technically a modified portion of the outsole, this portion is commonly considered as though it were a separate component located above the outsole and below the upper of the shoe. The midsole is normally constructed from such materials as ethylene vinyl acetate (EVA) and polyurethane (PU). Its primary function is to create a resilient and shock-absorbing layer to the footwear.
Shoes are typically constructed on a “last,” which is a solid form, usually made of plastic, over which the shoe upper is made. It is the last that determines the size, shape and certain style features of the shoe. The last is removed from the finished shoe prior to packing and then is re-used repeatedly in the construction of another shoe as part of the manufacturing process.
Within the footwear industry, it has long been recognized that a primary purpose and function of a shoe is to protect and support the human foot while the person performs his normal activities. Also, the increasing popularity of athletic sports, be it on a competitive or exercise level, has been accompanied by an ever-increasing number of new shoe designs and constructions that are intended to meet the needs of the individual when performing in the these events. Thus, a shoe such as an athletic shoe typically includes an outer sole to provide traction and foot protection; a midsole to provide cushioning; a shoe upper that is stitched or glued to the periphery of the outer sole and an insole to provide additional cushioning and support. The upper is intended to hold the foot of the wearer to the substance of the outer sole in order to provide a tight and comfortable fit and to prevent any sliding of the foot within the shoe interior.
The recent increase in shoe designs and modes of construction has particular value for persons involved in athletic endeavors, as well as for those engaging merely in walking and running for health and exercise purposes. Typically, it is understood within the footwear industry that when a person walks or runs one foot is on the ground in a “stance mode” while the other foot is moving through the air in a “swing mode”. Equally important, when in the stance mode, the person's foot recognizably moves through three successive movement phases when touching the ground. These movement phases are: the heel strike, the mid stance, and the toe off. Thus even in the stance mode, devices for cushioning should protect the human foot and shock absorption in order to control the compression forces generated by the person's foot upon the shoe.
The concept of providing cushioning and shock absorption for the foot is well known and often used, particularly within athletic footwear, to decrease the intense and repetitious impact which occurs during short time intervals in these activities. In addition, however, it is recognized also that foot cushioning systems can and often are beneficially incorporated into other types of footwear articles, including dress shoes, boots, sandals, as well as for athletic shoes, to provide better foot protection.
A wide variety of devices have been created in the footwear industry either to cushion the foot and/or to absorb the shock of the foot striking the ground. One early approach for impact absorption utilized blocks of compressible padding material; and many kinds of footwear have been constructed using cotton padding, horse hair padding, rubber, plastic foam, and the like as cushions. Within these designs, the inherent resilience of the compressible padding material is utilized to absorb and disperse the impact of the foot striking the ground. These compressible padding materials, however, present multiple problems. First, these materials are relatively inefficient in their ability to absorb shock and cushion the foot. Second, the materials typically become compacted after repeated use and often lose their cushioning properties. Third, with severe foot impact uses, these designs allow a full compression of the material and “bottom out” quickly, thereby transmitting the severe impact forces to the wearer's foot and body. In addition, when made thicker to avoid this third problem, these materials often become unstable, can become cumbersome and heavy, and typically interfere with the foot in performance of the exercise or physical routine.
More recently, manufacturers of athletic and running shoes have added other kinds of materials to cushion the person's foot when standing, walking, or running. Initially, foam of varying chemical composition was added to the shoe for cushioning and shock absorption purposes. Subsequently, shoe manufacturers developed other alternatives to foam-based cushioning systems because it was recognized that foam became permanently compressed with repeated use and thus ceased to perform the cushioning function. Other alternative designs for shock absorption and foot cushioning were also utilized with varying degrees of success. These included the use of compressed gas as the means to cushion the wearer's foot; the use of polyurethane elastomers as the cushioning material; a construction design having multiple layers of air cushioning; and the use of thermoplastic hollow tubes encapsulating a fluid or gas such as a freon.
Still other attempts to cushion the foot housed within a shoe are illustrated by the following: U.S. Pat. Nos. 5,070,629 and 5,561,920 describing an energy return system using a rigid frame construction and torsional rigidity bar in the mid foot area which provides cushioning and stability; U.S. Pat. No. 5,680,714 which describes the use of a plurality of elastic strips running at an angle across the shoe from one side to the other as a resilient return portion for shock absorption; U.S. Pat. No. 6,127,010 which discloses a shock absorbing cushioning device comprised of a compressible insert encapsulated within an elastomeric barrier member positioned within the outsole; and U.S. Pat. Nos. 6,195,915 and 6,330,757 which describe an outsole which is operative to store and release energy resulting from compression forces generated by the person's weight and is intended to be joined to standard footwear uppers.
The flaw in all of these conventionally available technologies and footwear designs is that each of these modifications concern themselves solely with the conventional outsole of the shoe to compress more efficiently; but none of these design modifications allow the upper of the shoe to assist in either a deceleration of the compression forces and shock upon the foot or in a cushioning the foot itself. Instead, all of the conventional footwear designs are structured and manufactured to hold the person's foot in a static position while the outsole, and possibly the midsole, of the shoe contorts to lessen the impact shock. Thus, the conventional footwear constructions are dedicated completely to materials and designs intended for compression within the outsole/midsole of the shoe; and none of the conventional footwear constructions allow the person's foot to either move or decelerate within the upper of the shoe in order to cushion the foot and to absorb the impact shock.